This invention relates to methods of reclaiming waste fiber-reinforced asphalt sheet material, especially roofing such as shingles and built-up roofing material, and to reclaimed products of such waste. More particularly, the methods of the invention are applicable to the reclaiming of waste of which the fibers are inelastic and brittle, such as from fiberglass mat which currently is nearly exclusively the reinforcing base for asphalt sheet roofing produced in the United States. The products are produced from waste having its fiber content of this character and are useful in conventional processes of manufacture of the parent material from which the waste is derived.
In the last two decades, the composition of roofing, particularly shingles, has undergone substantial change, due to a variety of factors such as improvement of quality and durability, the escalating cost of asphalt, and the requirements of modern, high speed manufacturing machines. The paper or mat of organic fiber, usually cellulose, previously used for impregnation by the asphalt, has been replaced by most manufacturers with a mat of glass fibers and the amount of asphalt used has been reduced from more than 50 by weight to less than 25% by weight. This reduction was partly made possible by the non-porosity of the glass fibers versus porosity of the organic fibers. The organic fibers needed a low melting point asphalt saturant which they could absorb to prevent cellulose moisture uptake, in addition to the higher melting point asphalt needed for product coating and strength in both the former and present products. The amount of mineral filler has been substantially increased in the fiberglass reinforced product, with attendant more rigid size and material specifications.
When used roofing is included, the yearly tonnage of waste roofing is enormous. Roofing using glass fibers has not been on the market extensively for more than its normal life cycle, so that used roofing is still largely of the older, organic fiber type. Immediately of more importance to modern roofing manufacture is what to do about waste produced in manufacture. Waste in roofing manufacture, occurring mainly in the cutting of shingles, runs about five percent of the tonnage of saleable product, a significant factor when it is considered that about 75% of manufacturing cost is that of materials used. Added to this is the considerable cost of disposal.
With increasing pressures of ecology, acceptable landfill sites for dumping are limited and incinerating has become dubious. In addition, trucking to site is expensive. Waste shingles have been used to some extent as a substitute for some of the asphalt in road paving, but the economics are such that usually not even trucking cost will be paid for the waste. Processes are known or under development for solvent extraction of the asphalt, but the economics of such processes are doubtful, particularly applied to glass-fibered waste with its lower asphalt content than the organic fibered product.
Methods have been proposed for reclaiming whole roofing manufacture waste, which are said to produce a reclaimed product useful in new roofing manufacture. U.S. Pat. No. 1,732,281 discloses such a method in which small pieces of the roofing of the then organic fiber type are subjected to the shearing action of alternate rotary and fixed knives, which break up the fiber mat and distribute the fiber and filler throughout the asphalt. The product is said to be useful as a molding compound, which sets to a rigid state and may be used as the core of special, molded shingles. U.S. Pat. No. 2,368,371 subjects roofing manufacture waste of the organic fiber type to the successive action of three hammermills, combines fractions from each mill and agitates the mix in hot asphalt. The process is said to disintegrate the fibrous material "into fine fibers or fibrillas". While the product is said to be useful in the production of asphalt products such as shingles, no details of a suitable manufacturing process are indicated.
Despite any suggestions of the prior art, we are aware of no manufacture of roofing which recycles 100% of the waste produced therein, it is believed because no method has been known by which all the components of the waste could be rendered suitable to meet the specifications for materials that can be satisfactorily used in the manufacturing process. There is a great and ever more pressing need for an economical method of treating roofing manufacture waste to provide products meeting all specifications for use in the manufacturing process.